Compounds for the photodecontamination of pathogens in blood

ABSTRACT

Psoralen compound compositions are synthesized which have substitutions on the 4, 4′, 5′, and 8 positions of the psoralen, which yet permit their binding to nucleic acid of pathogens. Reaction conditions that photoactivate these bound psoralens result in covalent crosslinking to nucleic acid, thereby inactivating the pathogen. Higher psoralen binding levels and lower mutagenicity results in safer, more efficient, and reliable inactivation of pathogens. In addition to the psoralen compositions, the invention contemplates inactivating methods using the new psoralens.

[0001] This application is a continuation of U.S. patent application Ser. No. 09/767,611, filed Jan. 22, 2001, which is a continuation of U.S. patent application Ser. No. 09/375,340, filed Aug. 16, 1999, which is a continuation of U.S. patent application Ser. No. 09/050,882, filed Mar. 30, 1998, which is a continuation of U.S. patent application Ser. No. 08/342,366, filed Nov. 18, 1994, which is a divisional application of U.S. application Ser. No. 08/083,459, filed Jun. 28, 1993, now issued U.S. Pat. No. 5,399,719.

FIELD OF THE INVENTION

[0002] The present invention also provides methods of using new and known compounds to inactivate pathogens in health related products to be used in vivo and in vitro, and in particular, blood products.

BACKGROUND

[0003] Although improved testing methods for hepatitis B (HBV), hepatitis C (HCV), and human immunodeficiency virus (HIV) have markedly reduced the incidence of transfusion associated diseases, other viral, bacterial, and protozoal agents are not routinely tested for, and remain a potential threat to transfusion safety. Schmunis, G. A., Transfusion 31:547-557 (1992). In addition, testing will not insure the safety of the blood supply against future unknown pathogens that may enter the donor population resulting in transfusion associated transmission before sensitive tests can be implemented.

[0004] The recent introduction of a blood test for HCV will reduce transmission of this virus; however, it has a sensitivity of only 67% for detection of probable infectious blood units. HCV is responsible for 90% of transfusion associated hepatitis. It is estimated that, with the test in place, the risk of infection is 1 out of 3300 units transfused.

[0005] Further, while more sensitive seriological assays are in place for HIV-1 and HBV, these agents can nonetheless be transmitted by seronegative blood donors. International Forum: Vox Sang 32:346 (1977). Ward, J. W., et al., N. Engl. J. Med., 318:473 (1988). Up to 10% of total transfusion-related hepatitis and 25% of severe icteric cases are due to the HBV transmitted by hepatitis B surface antigen (HBasAg) negative donors. Vox Sang 32:346 (1977). To date, fifteen cases of transfusion-associated HIV infections have been reported by the Center for Disease Control (CDC) among recipients of blood pretested negative for antibody to HIV-1.

[0006] Even if seroconversion tests were a sufficient screen, they may not be practical in application. For example, CMV (a herpes virus) and parvo B 19 virus in humans are common. When they occur in healthy, immunocompetent adults, they nearly always result in asymptomatic seroconversion. Because such a large part of the population is seropositive, exclusion of positive units would result in substantial limitation of the blood supply.

[0007] An alternative approach to eliminate transmission of viral diseases through blood products is to develop a means to inactivate pathogens in transfusion products. Development of an effective technology to inactivate infectious pathogens in blood products offers the potential to improve the safety of the blood supply, and perhaps to slow the introduction of new tests, such as the HIV-2 test, for low frequency pathogens. Ultimately, decontamination technology could significantly reduce the cost of blood products and increase the availability of scarce blood products. Furthermore, decontamination may extend the storage life of platelet concentrates which, according to Goldman M. and M. A. Blajchman, Transfusion Medicine Reviews. V: 73-83 (1991), are currently limited by potential bacterial contamination.

[0008] Several methods have been reported for the inactivation or elimination of viral agents in erythrocyte-free blood products. Some of these techniques, such as heat (Hilfenhous, J., et al., J. Biol. Std. 70:589 (1987)), solvent/detergent treatment (Horowitz, B., et al., Transfusion 25:516 (1985)), gamma-irradiation (Moroff, G., et al., Transfusion 26:453 (1986)), UV radiation combined with beta propriolactone, (Prince A. M., et al., Reviews of Infect Diseases 5:92-107 (1983) Prince A. M., et al., Reviews of Infect Diseases 5:92-107 (1983)), visible laser light in combination with hematoporphyrins (Matthews J. L., et al., Transfusion 28:81-83 (1988); North J., et al., Transfusion 32:121-128 (1992)), use of the photoactive dyes aluminum phthalocyananine and merocyanine 540 (Sieber F., et al. Blood 73:345-350 (1989); Rywkin S., et al., Blood 78 (Suppl 1):352a (Abstract) (1991)) or UV alone (Proudouz, K. N., et al., Blood 70:589 (1987)) are completely incompatable with maintainance of platelet function.

[0009] Other methods inactivate viral agents by using known furocoumarins, such as psoralens, in the presence of ultra-violet light. Psoralens are tricyclic compounds formed by the linear fusion of a furan ring with a coumarin. Psoralens can intercalate between the base pairs of double-stranded nucleic acids, forming covalent adducts to pyrimidine bases upon absorption of long wave ultraviolet light (UVA). G. D. Cimino et al., Ann. Rev. Biochem. 54:1151 (1985); Hearst et al., Quart. Rev. Biophys. 17:1 (1984). If there is a second pyrimidine adjacent to a psoralen-pyrimidine monoadduct and on the opposite strand, absorption of a second photon can lead to formation of a diadduct which functions as an interstrand crosslink. S. T. Isaacs et al., Biochemistry 16:1058 (1977); S. T. Isaacs et al., Trends in Photobiology (Plenum) pp. 279-294 (1982); J. Tessman et al., Biochem. 24:1669 (1985); Hearst et al., U.S. Pat. Nos. 4,124,598, 4,169,204, and 4,196,281, hereby incorporated by reference.

[0010] The covalently bonded psoralens act as inhibitors of DNA replication and thus have the potential to stop the replication process. Due to this DNA binding capability, psoralens are of particular interest in relation to solving the problems of creating and maintaining a safe blood supply. Some known psoralens have been shown to inactivate viruses in some blood products. H. J. Alter et al., The Lancet (ii:1446) (1988); L. Lin et al., Blood 74:517 (1989) (decontaminating platelet concentrates); G. P. Wiesehahn et al., U.S. Pat. Nos. 4,727,027 and 4,748,120, hereby incorporated by reference, describe the use of a combination of 8-methoxypsoralen (8-MOP) and irradiation. P. Morel et al., Blood Cells 18:27 (1992) show that 300 ug/mL of 8-MOP together with ten hours of irradiation with ultraviolet light can effectively inactivate viruses in human serum. Similar studies using 8-MOP and aminomethyltrimethyl psoralen (AMT) have been reported by other investigators. Dodd R Y, et al., Transfusion 31:483-490 (1991): Margolis-Nunno, H., et al., Thromb Haemostas 65:1162 (Abstract) (1991). Indeed, the photoinactivation of a broad spectrum of microorganisms has been established, including HBV, HCV, and HIV. [Hanson C. V., Blood Cells: 18:7-24 (1992); Alter, H. J., et al., The Lancet ii:1446 (1988); Margolis-Nunno H. et al., Thromb Haemostas 65:1162 (Abstract) (1991).]

[0011] Psoralen photoinactivation is only feasible if the ability of the psoralen to inactivate viruses is sufficient to ensure a safety margin in which complete inactivation will occur. On the other hand, the psoralen must not be such that it will cause damage to blood cells. Previous compounds and protocols have necessitated the removal of molecular oxygen from the reaction before exposure to light, to prevent damage to blood products from oxygen radicals produced during irradiation See L. Lin et al., Blood 74:517 (1989); U.S. Pat. No. 4,727,027, to Wiesehahn. This is a costly and time consuming procedure.

[0012] Finally, some commonly known compounds used in PCD cause undesirable mutagenic effects which appears to increase with increased ability to kill virus. In other words, the more effective the known compounds are at inactivating viruses, the more mutagenic the compounds are, and thus, the less useful they at any point in an inactivation system of products for in vivo use. A new psoralen compound is needed which displays improved ability to inactivate pathogens and low mutagenicity, thereby ensuring safe and complete inactivation of pathogens in blood decontamination methods.

SUMMARY OF THE INVENTION

[0013] The present invention provides new psoralens and methods of synthesis of new psoralens having enhanced ability to inactivate pathogens in the presence of ultraviolet light which is not linked to mutagenicity. The present invention also provides methods of using new and known compounds to inactivate pathogens in health related products to be used in vivo and in vitro, and particularly, in blood products and blood products in synthetic media.

[0014] With respect to new compounds, the present invention contemplates psoralen compounds, comprising: a) a substituent R₁ on the 4′ carbon atom, selected from the group comprising: —(CH₂)_(u)—NH₂, —(CH₂)_(w)—R₂—(CH₂)_(z)—NH₂, —(CH₂)_(w)—R₂—(CH₂)_(x)—R₃—(CH₂)_(z)—NH₂, and —(CH₂)_(w)—R₂—(CH₂)_(x)—R₃—(CH₂)_(y)—R₄—(CH₂)_(z)—NH₂; wherein R₂, R₃, and R₄ are independently selected from the group comprising O and NH, in which u is a whole number from 1 to 10, w is a whole number from 1 and 5, x is a whole number from 2 and 5, y is a whole number from 2 and 5, and z is a whole number from 2 and 6; and b) substituents R₅, R₆, and R₇ on the 4, 5′, and 8 carbon atoms respectively, independently selected from the group comprising H and (CH₂)_(v)CH₃, where v is a whole number from 0 to 5; or a salt thereof. Where an element is “independently selected” from a group, it means that the element need not be the same as other elements chosen from the same group.

[0015] The invention contemplates specific compounds of the above structure, wherein R₁ is —CH₂—O—(CH₂)₂—NH₂, and wherein R₅, R₆, and R₇ are all CH₃, wherein R₁ is —CH₂—O—(CH₂)₂—O—(CH₂)₂—NH₂, and R₅, R₆, and R₇ are all CH₃, wherein R₁ is —CH₂—O—(CH₂)₂—O—(CH₂)₂—NH—(CH₂)₄—NH₂, and R₅, R₆, and R₇ are all CH₃, wherein R₁ is CH₂—NH—(CH₂)₄—NH₂, and R₅, R₆, and R₇ are all CH₃, and wherein R₁ is CH₂—NH—(CH₂)₃—NH—(CH₂)₄—NH—(CH₂)₃—NH₂, and R₅, R₆, and R₇ are all CH₃.

[0016] The present invention also contemplates psoralen compounds, comprising: a) a substituent R₁ on the 5′ carbon atom, selected from the group comprising: —(CH₂)_(u)—NH₂, —(CH₂)_(w)—R₂—(CH₂)_(z)—NH₂, —(CH₂)_(w)—R₂—(CH₂)_(x)—R₃—(CH₂)_(z)—NH₂, and —(CH₂)_(w)—R₂—(CH₂)_(x)—R₃—(CH₂)_(y)—R₄—(CH₂)_(z)—NH₂; wherein R₂, R₃, and R₄ are independently selected from the group comprising O and NH, and in which u is a whole number from 1 to 10, w is a whole number from 1 to 5, x is a whole number from 2 to 5, y is a whole number from 2 to 5, and z is a whole number from 2 to 6; and, b) substituents R₅, R₆, and R₇ on the 4, 4′, and 8 carbon atoms respectively, independently selected from the group comprising H and (CH₂)_(v)CH₃, where v is a whole number from 0 to 5, and where when R₁ is —(CH₂)_(u)—NH₂, R₆ is H; or a salt thereof. The present invention contemplate a specific compound having the above structure, wherein R₁ is —CH₂—NH—(CH₂)₄—NH₂, and R₅, R₆, and R₇ are all CH₃.

[0017] The present invention also contemplates psoralen compounds, comprising: a) a substituent R₁ on the 5′ carbon atom, selected from the group comprising: —(CH₂)_(u)—NH₂, —(CH₂)_(w)—R₂—(CH₂)_(z)—NH₂, —(CH₂)_(w)—R₂—(CH₂)_(x)—R₃—(CH₂)_(z)—NH₂, and —(CH₂)_(w)—R₂—(CH₂)_(x)—R₃—(CH₂)_(y)—R₄—(CH₂)_(z)—NH₂; wherein R₂, R₃, and R₄ are independently selected from the group comprising O and NH, and in which u is a whole number from 3 to 10, w is a whole number from 1 to 5, x is a whole number from 2 to 5, y is a whole number from 2 to 5, and z is a whole number from 2 to 6; and, b) substituents R₅, R₆, and R₇ on the 4, 4′, and 8 carbon atoms respectively, independently selected from the group comprising H and (CH₂)_(v)CH₃, where v is a whole number from 0 to 5; or a salt thereof. The present invention contemplates a specific compound having the above structure, wherein R₁ is —CH₂—NH—(CH₂)₄—NH₂, and R₅, R₆, and R₇ are all CH₃.

[0018] With respect to methods for synthesizing new compounds substituted at the 4′ position of the psoralen, the present invention contemplates a method of synthesizing 4′-(w-amino-2-oxa)alkyl-4,5′,8-trimethylpsoralen, comprising the steps: a) providing 4′-(w-hydroxy-2-oxa)alkyl-4,5′,8-trimethylpsoralen; b) treating 4′-(w-hydroxy-2-oxa)alkyl-4,5′,8-trimethylpsoralen with a base and methanesulfonyl chloride so that 4′-(w-methanesulfonyloxy-2-oxa)alkyl-4,5′,8-trimethylpsoralen is produced; c) treating 4′-(w-methanesulfonyloxy-2-oxa)alkyl-4,5′,8-trimethylpsoralen with sodium azide, so that 4′-(w-azido-2-oxa)alkyl-4,5′,8-trimethylpsoralen is produced, and d) reducing 4′-[(w-azido-2-oxa)alkyl-4,5′,8-trimethylpsoralen so that 4′-[(w-amino-2-oxa)alkyl-4,5′,8-trimethylpsolaren is produced.

[0019] The present invention further contemplates a method of synthesizing a compound of the structure which has a substituent R₁ on the 4′ position of the psoralen, described above, where R₁ comprises —(CH₂)—O—(CH₂)_(x)—O—(CH₂)_(z)—NH₂, where x=z, comprising the steps: a) providing a 4′-halomethyl-4,5′,8-trimethyl psoralen selected from the group comprising 4′-chloromethyl-4,5′,8-trimethyl psoralen, 4′-bromomethyl-4,5′,8-trimethyl psoralen, and 4′-iodomethyl-4,5′,8-trimethyl psoralen; b) treating said 4′-halomethyl-4,5′,8-trimethyl psoralen with HO(CH₂)_(x)O(CH₂)_(z)OH so that 4′-(w-hydroxy-2,n-dioxa)alkyl-4,5′,8-trimethylpsoralen is produced, where n=x+3; c) treating said 4′-(w-hydroxy-2,n-dioxa)alkyl-4,5′,8-trimethylpsoralen with a base and methanesulfonyl chloride so that 4′-(w-methylsulfonyloxy-2,n-dioxa)alkyl-4,5′,8-trimethylpsoralen is produced; d) treating, 4′-(w-methanesulfonyloxy-2,n-dioxa)alkyl-4,5′,8-trimethylpsoralen with sodium azide so that 4′-(w-azido-2,n-dioxa)alkyl-4,5′,8-trimethylpsoralen is produced; and e) reducing 4′-(w-azido-2,n-dioxa)alkyl-4,5′,8-trimethylpsoralen so that 4′-(w-amino-2,n-dioxa)alkyl-4,5′,8-trimethylpsoralen is produced.

[0020] The present invention also contemplates a method of synthesizing 4′-(12-amino-8-aza-2,5-dioxa)dodecyl-4,5′,8-trimethylpsoralen, comprising the steps: a) providing a 4′-halomethyl-4,5′,8-trimethylpsoralen, selected from the group comprising 4′-chloromethyl-4,5′,8-trimethyl psoralen, 4′-bromomethyl-4,5′,8-trimethyl psoralen, and 4′-iodomethyl-4,5′,8-trimethyl psoralen; b) treating said 4′-halomethyl-4,5′,8-trimethyl psoralen with diethylene glycol so that 4′-(7-hydroxy-2,5-dioxa)heptyl-4,5′,8-trimethylpsoralen is produced; c) treating 4′-(7-hydroxy-2,5-dioxa)heptyl-4,5′,8-trimethylpsolaren with a base and methanesulfonyl chloride so that 4′-(7-methanesulfonyloxy-2,5-dioxa)heptyl-4,5′,8-trimethylpsoralen is produced; d) treating 4′-(7-methanesulfonyloxy-2,5-dioxa)heptyl-4,5′,8-trimethylpsoralen with 1, 4-diaminobutane so that 4′-(12-amino-8-aza-2,5-dioxa)dodecyl-4,5′,8-trimethylpsoralen is produced.

[0021] The present invention contemplates a method of synthesizing 4′-(w-amino-2-aza)alkyl-4,5′,8-trimethylpsoralen, comprising: a) providing 4′-halomethyl-4,5′,8-trimethylpsoralen, selected from the group comprising 4′-chloromethyl-4,5′,8-trimethyl psoralen, 4′-bromomethyl-4,5′,8-trimethyl psoralen, and 4′-iodomethyl-4,5′,8-trimethyl psoralen; b) treating said 4′-halomethyl-4,5′,8-trimethylpsoralen with 1,w-aminoalkane to produce 4′-(w-diamino-2-aza)alkyl-4,5′,8-trimethylpsoralen.

[0022] The present invention additionally contemplates a method of synthesizing 4′-(14-amino-2,6,11-triaza)tetradecyl-4,5′,8-trimethylpsoralen, comprising: a) providing 4,5′,8-trimethylpsoralen-4′-carboxaldehyde; b) treating 4,5′,8-trimethylpsoralen-4′-carboxaldehyde with spermine and a reducing agent to produce 4′-(14-amino-2,6,11-triaza)tetradecane-4,5′,8-trimethylpsoralen.

[0023] Finally, the present invention contemplates the following method of synthesizing 5′-(w-amino-2-aza)alkyl-4,4′,8-trimethylpsoralen comprising: a) providing a 5′-halomethyl-4,4′,8-trimethylpsoralen, selected from the group comprising 5′-chloromethyl-4,4′,8-trimethyl psoralen, 5′-bromomethyl-4,4′,8-trimethyl psoralen, and 5′-iodomethyl-4,4′,8-trimethyl psoralen; b) treating said 5′-halomethyl-4,4′,8-trimethylpsoralen with a 1,w-diaminoalkane to produce 5′-(w-amino-2-aza)alkyl-4,4′,8-trimethylpsoralen.

[0024] The present invention contemplates methods of inactivating microorganisms in blood preparations, comprising, in the following order: a) providing, in any order, i) a compound from the group comprising 4′-primaryamino-substituted psoralens and 5′-primaryamino-substituted psoralens; ii) photoactivating means for photoactivating said compounds; and iii) a blood preparation suspected of being contaminated with a pathogen having nucleic acid; b) adding said compound to said blood preparation; and c) photoactivating said compound, so as to inactivate said pathogen.

[0025] The pathogen can be single cell or multicellular organisms, such as bacteria, fungi, mycoplasma and protozoa, or viruses. The pathogen can comprise either DNA or RNA, and this nucleic acid can be single stranded or double stranded. In one embodiment, the blood preparation is either platelets or plasma.

[0026] The present invention contemplates that the photoactivating means comprises a photoactivation device capable of emitting a given intensity of a spectrum of electromagnetic radiation comprising wavelengths between 180 nm and 400 nm, and in particular, between 320 nm and 380 nm. It is preferred that the intensity is between 1 and 30 mW/cm² (e.g., between 10 and 20 mW/cm²) and that the mixture is exposed to this intensity for between one second and thirty minutes (e.g., ten minutes).

[0027] The present invention contemplates embodiments wherein said blood preparation is in a synthetic media. In one embodiment, the concentration of compound is between 0.1 and 250 μM. In a preferred embodiment, the compound is added to said blood preparation at a concentration of between 10 and 150 μM.

[0028] The present invention contemplates embodiments of the methods where inactivation is performed without limiting the concentration of molecular oxygen. Furthermore, there is no need for the use of cosolvents (e.g., dimethyl sulphoxide (DMSO)) to increase compound solubility.

[0029] In one embodiment, the present invention contemplates methods of inactivating microorganisms in blood preparations, wherein the compound is a 4′-primaryamino-substituted psoralen, comprising: a) a substituent R₁ on the 4′ carbon atom, selected from the group comprising: —(CH₂)_(u)—NH₂, —(CH₂)_(w)—R₂—(CH₂)_(z)—NH₂, —(CH₂)_(w)—R₂—(CH₂)_(x)—R₃—(CH₂)_(z)—NH₂, and —(CH₂)_(w)—R₂—(CH₂)_(x)—R₃—(CH₂)_(y)—R₄—(CH₂)_(z)—NH₂; wherein R₂, R₃, and R₄ are independently selected from the group comprising O and NH, in which u is a whole number from 1 to 10, w is a whole number from 1 to 5, x is a whole number from 2 to 5, y is a whole number from 2 to 5, and z is a whole number from 2 to 6; and b) substituents R₅, R₆, and R₇ on the 4, 5′, and 8 carbon atoms respectively, independently selected from the group comprising H and (CH₂)_(v)CH₃, where v is a whole number from 0 to 5; or a salt thereof.

[0030] Alternatively, the present invention contemplates embodiments of the method of inactivation, wherein the compound is a 5′-primaryamino-substituted psoralen comprising: a) a substituent R₁ on the 5′ carbon atom, selected from the group comprising: —(CH₂)_(u)—NH₂, —(CH₂)_(w)—R₂—(CH₂)_(z)—NH₂, —(CH₂)_(w)—R₂—(CH₂)_(x)—R₃—(CH₂)_(z)—NH₂, and —(CH₂)_(w)—R₂—(CH₂)_(x)—R₃—(CH₂)_(y)—R₄—(CH₂)_(z)—NH₂; wherein R₂, R₃, and R₄ are independently selected from the group comprising O and NH, and in which u is a whole number from 1 to 10, w is a whole number from 1 to 5, x is a whole number from 2 to 5, y is a whole number from 2 to 5, and z is a whole number from 2 to 6; and, b) substituents R₅, R₆, and R₇ on the 4, 4′, and 8 carbon atoms respectively, independently selected from the group comprising H and (CH₂)_(v)CH₃, where v is a whole number from 0 to 5, and where when R₁ is selected from the group comprising —(CH₂)_(u)—NH₂, R₆ is H; or a salt thereof.

[0031] Alternatively, the present invention contemplates embodiments of the method of inactivation, wherein the compound is a 5′-primaryamino-substituted psoralen comprising: a) a substituent R₁ on the 5′ carbon atom, selected from the group comprising: —(CH₂)_(u)—NH₂, —(CH₂)_(w)—R₂—(CH₂)_(z)—NH₂, —(CH₃)_(w)—R₂—(CH₂)_(x)—R₃—(CH₂)_(z)—NH₂, and —(CH₂)_(w)—R₂—(CH₃)_(x)—R₃—(CH₂)_(y)—R₄—(CH₂)_(z)—NH₂; wherein R₂, R₃, and R₄ are independently selected from the group comprising O and NH, and in which u is a whole number from 3 to 10, w is a whole number from 1 to 5, x is a whole number from 2 to 5, y is a whole number from 2 to 5, and z is a whole number from 2 to 6; and, b) substituents R₅, R₆, and R₇ on the 4, 4′, and 8 carbon atoms respectively, independently selected from the group comprising H and (CH₂)_(v)CH₃, where v is a whole number from 0 to 5; or a salt thereof.

[0032] In one embodiment of the method of inactivation, at least two of the compounds are present. The present invention contemplates embodiments where the compound is introduced either in solution, such as water, saline, or a synthetic media, or in a dry formulation. The present invention also contemplates that the nucleic acid may be DNA or RNA, single stranded or double stranded.

DESCRIPTION OF THE DRAWINGS

[0033]FIG. 1 is a perspective view of one embodiment of the device of the present invention.

[0034]FIG. 2 is a cross-sectional view of the device shown in FIG. 1 along the lines of 2-2.

[0035]FIG. 3 is a cross-sectional view of the device shown in FIG. 1 along the lines of 3-3.

[0036]FIG. 4 is a cross-sectional view of the device shown in FIG. 1 along the lines of 4-4.

[0037]FIG. 5A is a diagram of the synthesis pathways and chemical structures of compounds 8, 13, and 14 of the present invention.

[0038]FIG. 5B is a diagram of the synthesis pathways and chemical structures of compounds 2, 4, and 7 of the present invention.

[0039]FIG. 5C is a diagram of the synthesis pathways and chemical structures of compounds 1, 5, 6, 9, and 10 of the present invention.

[0040]FIG. 5D is a diagram of the synthesis pathways and chemical structures of compounds 12 and 15 of the present invention.

[0041]FIG. 5E is a diagram of a synthesis pathways and the chemical structure of compound 3 of the present invention.

[0042]FIG. 5F is a diagram of a synthesis pathways and the chemical structure of compounds 16 and 17 of the present invention.

[0043]FIG. 6 shows the impact of concentration on the log kill of R17 when Compounds 1-3 of the present invention are photoactivated.

[0044]FIG. 7 shows the impact of concentration on the log kill of R17 when Compounds 3-6 of the present invention are photoactivated.

[0045]FIG. 8 shows the impact of concentration on the log kill of R17 when Compounds 2 and 6 of the present invention are photoactivated.

[0046]FIG. 9 shows the impact of concentration on the log kill of R17 when Compounds 6 and 18 of the present invention are photoactivated.

[0047]FIG. 10 shows the impact of concentration on the log kill of R17 when Compound 16 of the present invention is photoactivated.

[0048]FIG. 11 shows the impact of varying Joules of irradiation on the log titer of R17 for Compound 6 of the present invention.

[0049]FIG. 12 shows the impact of varying Joules of irradiation on the log titer of R17 for Compounds 7, 9 and 10 of the present invention.

[0050]FIG. 13 shows the impact of varying Joules of irradiation on the log titer of R17 Compounds 7 and 12 of the present invention.

[0051]FIG. 14 shows the impact of varying Joules of irradiation on the log titer of R17 for Compound 15 of the present invention.

[0052]FIG. 15 shows the impact of varying Joules of irradiation on the log titer of R17 for Compound 17 of the present invention.

[0053]FIG. 16 shows the impact of varying Joules of irradiation on the log titer of R17 for Compounds 6 and 17 of the present invention.

[0054]FIG. 17 shows the impact of varying Joules of irradiation on the log titer of R17 for Compounds 6 and 15 of the present invention.

[0055]FIG. 18 shows the effect of varying the concentration of Compounds 2 and 6 of the present invention, in plasma.

[0056]FIG. 19 shows the effect of varying the concentration of Compounds 2 and 6 of the present invention, in synthetic medium.

[0057]FIG. 20A schematically shows the standard blood product separation approach used presently in blood banks.

[0058]FIG. 20B schematically shows an embodiment of the present invention whereby synthetic media is introduced to platelet concentrate prepared as in FIG. 20A.

[0059]FIG. 20C schematically shows one embodiment of the decontamination approach of the present invention applied specifically to platelet concentrate diluted with synthetic media as in FIG. 20B.

DESCRIPTION OF THE INVENTION

[0060] The present invention provides new psoralens and methods of synthesis of new psoralens having enhanced ability to inactivate pathogens in the presence of ultraviolet light, which is not linked to mutagenicity. The new psoralens are effective against a wide variety of pathogens. The present invention also provides methods of using new and known compounds to inactivate pathogens in health related products to be used in vivo and in vitro, and in particular, blood products.

[0061] The inactivation methods of the present invention provide methods of inactivating pathogens, and in particular, viruses, in blood products prior to use in vitro or in vivo. In contrast with previous approaches, the method requires only short irradiation times and there is no need to limit the concentration of molecular oxygen.

[0062] The description of the invention is divided into the following sections: I) Photoactivation Devices, II) Compound Synthesis, III) Binding of Compounds to Nucleic Acid, IV) Inactivation of Contaminants, and V) Preservation of Biochemical Properties of Material Treated.

[0063] 1. Photoactivation Devices

[0064] The present invention contemplates devices and methods for photoactivation and specifically, for photoactivation of photoreactive nucleic acid binding compounds. The present invention contemplates devices having an inexpensive source of electromagnetic radiation that is integrated into a unit. In general, the present invention contemplates a photoactivation device for treating photoreactive compounds, comprising: a) means for providing appropriate wavelengths of electromagnetic radiation to cause photoactivation of at least one photoreactive compound; b) means for supporting a plurality of samples in a fixed relationship with the radiation providing means during photoactivation; and c) means for maintaining the temperature of the samples within a desired temperature range during photoactivation. The present invention also contemplates methods, comprising: a) supporting a plurality of sample containers, containing one or more photoreactive compounds, in a fixed relationship with a fluorescent source of electromagnetic radiation; b) irradiating the plurality of sample containers simultaneously with electromagnetic radiation to cause photoactivation of at least one photoreactive compound; and c) maintaining the temperature of the sample within a desired temperature range during photoactivation.

[0065] The major features of one embodiment of the device of the present invention involve: A) an inexpensive source of ultraviolet radiation in a fixed relationship with the means for supporting the sample containers, B) rapid photoactivation, C) large sample processing, D) temperature control of the irradiated samples, and E) inherent safety.

[0066] A. Electromagnetic Radiation Source

[0067] Many sources of ultraviolet radiation can be successfully used in decontamination protocols with psoralens. For example, some groups have irradiated sample from above and below by General Electric type F20T12-BLB fluorescent UVA bulbs with an electric fan blowing gently across the lights to cool the area. Alter, H. J., et al., The Lancet, 24:1446 (1988). Another group used Type A405-TLGW/05 long wavelength ultraviolet lamp manufactured by P. W. Allen Co., London placed above the virus samples in direct contact with the covers of petri dishes containing the samples, and was run at room temperature. The total intensity deliverd to the samples under these conditions was 1.3×10¹⁵ photons/sec cm² or 0.7 mW/cm² in the petri dish. Hearst, J. E., and Thiry, L., Nucleic Acids Research, 4:1339 (1977). However, without intending to be limited to any type of photoactivation device, the present invention contemplates several preferred arrangements for the photoactivation device, as follows.

[0068] A preferred photoactivation device of the present invention has an inexpensive source of ultraviolet radiation in a fixed relationship with the means for supporting the sample vessels. Ultraviolet radiation is a form of energy that occupies a portion of the electromagnetic radiation spectrum (the electromagnetic radiation spectrum ranges from cosmic rays to radio waves). Ultraviolet radiation can come from many natural and artificial sources. Depending on the source of ultraviolet radiation, it may be accompanied by other (non-ultraviolet) types of electromagnetic radiation (e.g., visible light).

[0069] Particular types of ultraviolet radiation are herein described in terms of wavelength. Wavelength is herein described in terms of nanometers (“nm”; 10⁻⁹ meters). For purposes herein, ultraviolet radiation extends from approximately 180 nm to 400 nm. When a radiation source, by virtue of filters or other means, does not allow radiation below a particular wavelength (e.g., 320 nm), it is said to have a low end “cutoff” at that wavelength (e.g., “a wavelength cutoff at 300 nanometers”). Similarly, when a radiation source allows only radiation below a particular wavelength (e.g., 360 nm), it is said to have a high end “cutoff” at that wavelength (e.g., “a wavelength cutoff at 360 nanometers”).

[0070] For any photochemical reaction it is desired to eliminate or least minimize any deleterious side reactions. Some of these side reactions can be caused by the excitation of endogenous chromophores that may be present during the photoactivation procedure. In a system where only nucleic acid and psoralen are present, the endogenous chromophores are the nucleic acid bases themselves. Restricting the photoactivation process to wavelengths greater than 320 nm minimizes direct nucleic acid damage since there is very little absorption by nucleic acids above 313 nm.

[0071] In human serum or plasma, for example, the nucleic acid is typically present together with additional biological constituents. If the biological fluid is just protein, the 320 nm cutoff will be adequate for minimizing side reactions (aromatic amino acids do not absorb above 320 nm). If the biological fluid includes other analytes, there may be constituents that are sensitive to particular wavelengths of light. In view of the presence of these endogenous constituents, it is intended that the device of the present invention be designed to allow for irradiation within a small range of specific and desirable wavelengths, and thus avoid damage blood components. The preferred range of desirable wavelengths is between 320 and 350 nm.

[0072] Some selectivity can be achieved by choice of commercial irradiation sources. For example, while typical fluorescent tubes emit wavelengths ranging from 300 nm to above 400 nm (with a broad peak centered around 360 nm), BLB type fluorescent lamps are designed to remove wavelengths above 400 nm. This, however, only provides an upper end cutoff.

[0073] In a preferred embodiment, the device of the present invention comprises an additional filtering means. In one embodiment, the filtering means comprises a glass cut-off filter, such as a piece of Cobalt glass. In another embodiment, the filtering means comprises a liquid filter solution that transmits only a specific region of the electromagnetic spectrum, such as an aqueous solution of Co(No3)2. This salt solution yields a transmission window of 320-400 nm. In a preferred embodiment, the aqueous solution of Co(No3)2 is used in combination with NiSO4 to remove the 365 nm component of the emission spectrum of the fluorescent or arc source employed. The Co—Ni solution preserves its initial transmission remarkably well even after tens of hours of exposure to the direct light of high energy sources.

[0074] It is not intended that the present invention be limited by the particular filter employed. Several inorganic salts and glasses satisfy the necessary requirements. For example, cupric sulfate is a most useful general filter for removing the infra-red, when only the ultraviolet is to be isolated. Its stability in intense sources is quite good. Other salts are known to one skilled in the art. Aperture or reflector lamps may also be used to achieve specific wavelengths and intensities.

[0075] When ultraviolet radiation is herein described in terms of irradiation, it is expressed in terms of intensity flux (milliwatts per square centimeter or “mW cm-2”). “Output” is herein defined to encompass both the emission of radiation (yes or no; on or off) as well as tile level of irradiation. In a preferred embodiment, intensity is monitored at 4 locations: 2 for each side of the plane of irradiation.

[0076] A preferred source of ultraviolet radiation is a fluorescent source. Fluorescence is a special case of luminescence. Luminescence involves the absorption of electromagnetic radiation by a substance and the conversion of the energy into radiation of a different wavelength. With fluorescence, the substance that is excited by the electromagnetic radiation returns to its ground state by emitting a quantum of electromagnetic radiation. While fluorescent sources have heretofore been thought to be of too low intensity to be useful for photoactivation, in one embodiment the present invention employs fluorescent sources to achieve results thus far achievable on only expensive equipment.

[0077] As used here, fixed relationship is defined as comprising a fixed distance and geometry between the sample and the light source during the sample irradiation. Distance relates to the distance between the source and the sample as it is supported. It is known that light intensity from a point source is inversely related to the square of the distance from the point source. Thus, small changes in the distance from the source can have a drastic impact on intensity. Since changes in intensity can impact photoactivation results, changes in distance are avoided in the devices of the present invention. This provides reproducibility and repeatability.

[0078] Geometry relates to the positioning of the light source. For example, it can be imagined that light sources could be placed around the sample holder in many ways (on the sides, on the bottom, in a circle, etc.). The geometry used in a preferred embodiment of the present invention allows for uniform light exposure of appropriate intensity for rapid photoactivation. The geometry of a preferred device of the present invention involves multiple sources of linear lamps as opposed to single point sources. In addition, there are several reflective surfaces and several absorptive surfaces. Because of this complicated geometry, changes in the location or number of the lamps relative to the position of the samples to be irradiated are to be avoided in that such changes will result in intensity changes.

[0079] B. Rapid Photoactivation

[0080] The light source of the preferred embodiment of the present invention allows for rapid photoactivation. The intensity characteristics of the irradiation device have been selected to be convenient with the anticipation that many sets of multiple samples may need to be processed. With this anticipation, a fifteen minute exposure time or less is a practical goal.

[0081] In designing the devices of the present invention, relative position of the elements of the preferred device have been optimized to allow for fifteen minutes of irradiation time, so that, when measured for the wavelengths between 320 and 350 nanometers, an intensity flux greater than approximately 1 mW cm-2 is provided to the sample vessels.

[0082] C. Processing of Large Numbers of Samples

[0083] As noted, another important feature of the photoactivation devices of the present invention is that they provide for the processing of large numbers of samples. In this regard, one element of the devices of the present invention is a means for supporting a plurality of sample containers. In the preferred embodiment of the present invention the supporting means comprises a tube rack placed between two banks of lights. By accepting commonly used commercially available tubes, the device of the present invention allows for convenient processing of large numbers of samples.

[0084] D. Temperature Control

[0085] As noted, one of the important features of the photoactivation devices of the present invention is temperature control. Temperature control is important because the temperature of the sample in the sample at the time of exposure to light can dramatically impact the results. For example, conditions that promote secondary structure in nucleic acids also enhance the affinity constants of many psoralen derivatives for nucleic acids. Hyde and Hearst, Biochemistry, 17, 1251 (1978). These conditions are a mix of both solvent composition and temperature. With single stranded 5S ribosomal RNA, irradiation at low temperatures enhances the covalent addition of HMT to 5S rRNA by two fold at 4° C. compared to 20° C. Thompson et al., J. Mol. Biol. 147:417 (1981). Even further temperature induced enhancements of psoralen binding have been reported with synthetic polynucleotides. Thompson et al., Biochemistry 21:1363 (1982).

[0086] E. Inherent Safety

[0087] Ultraviolet radiation can cause severe burns. Depending on the nature of the exposure, it may also be carcinogenic. The light source of a preferred embodiment of the present invention is shielded from the user. This is in contrast to the commercial hand-held ultraviolet sources as well as the large, high intensity sources. In a preferred embodiment, the irradiation source is contained within a housing made of material that obstructs the transmission of radiant energy (i.e., an opaque housing). No irradiation is allowed to pass to the user. This allows for inherent safety for the user.

[0088] II. Compound Synthesis

[0089] A. Photoactivation Compounds in General

[0090] “Photoactivation compounds” (or “photoreactive compounds”) defines a family of compounds that undergo chemical change in response to electromagnetic radiation. Table 1 is a partial list of photoactivation compounds. TABLE 1 Photoactivation Compounds Actinomycins Anthracyclinones Anthramycin Benzodipyrones Fluorenes And Fluorenones Furocoumarins Mitomycin Monostral Fast Blue Norphillin A Many Organic Dyes Not Specifically Listed Phenanthridines Phenazathionium Salts Phenazines Phenothiazines Phenylazides Quinolines Thiaxanthenones

[0091] The species of photoreactive compounds described herein is commonly referred to as the furocoumarins. In particular, the present invention contemplates those compounds described as psoralens: [7H-furo(3,2-g)-(1)-benzopyran-7-one, or b-lactone of 6-hydroxy-5-benzofuranacrylic acid], which are linear:

[0092] and in which the two oxygen residues appended to the central aromatic moiety have a 1, 3 orientation, and further in which the furan ring moiety is linked to the 6 position of the two ring coumarin system. Psoralen derivatives are derived from substitution of the linear furocoumarin at the 3, 4, 5, 8, 4′, or 5′ positions.

[0093] 8-Methoxypsoralen (known in the literature under various named, e.g., xanthotoxin, methoxsalen, 8-MOP) is a naturally occuring psoralen with relatively low photoactivated binding to nucleic acids and low mutagenicity in the Ames assay, described in the following experimental section. 4′-Aminomethyl-4,5′,8-trimethylpsoralen (AMT) is one of most reactive nucleic acid binding psoralen derivatives, providing up to 1 AMT adduct per 3.5 DNA base pairs. S. T. Isaacs, G. Wiesehahn and L. M. Hallick, NCI Monograph 66:21 (1984). However, AMT also exhibits significant levels of mutagenicity. A new group of psoralens was desired which would have the best characteristics of both 8-MOP and AMT: low mutagenicity and high nucleic acid binding affinity, to ensure safe and thorough inactivation of pathogens. The compounds of the present invention were designed to be such compounds.

[0094] “4′-primaryamino-substituted psoralens” are defined as psoralen compounds which have an NH₂ group linked to the 4′-position of the psoralen by a hydrocarbon chain having a total length of 2 to 20 carbons, where 0 to 6 of those carbons are independently replaced by NH or O, and each point of replacement is separated from each other point of replacement by at least two carbons, and is separated from the psoralen by at least one carbon.

[0095] “5′-primaryamino-substituted psoralens” are defined as psoralen compounds which have an NH₂ group linked to the 5′-position of the psoralen by a hydrocarbon chain having a total length of 1 to 20 carbons, where 0 to 6 of those carbons are independently replaced by NH or O, and each point of replacement is separated from each other point of replacement by at least two carbons, and is separated from the psoralen by at least one carbon.

[0096] B. Synthesis of the Psoralens

[0097] The present invention contemplates synthesis methods for the novel compounds of the present invention. Several specific examples of the schemes discussed in this section are shown in FIGS. 5A-5F. For ease of reference, the compounds in these figures have been numbered from Compound 1 to Compound 17. For the subclass of the linear psoralens, 4,5′,8-trialkylpsoralens can be made as follows. The 4,8-dialkylcoumarins are prepared from 2-alkylresorcinols and a 3-oxoalkanoate ester by the Pechmann reaction (Organic Reactions Vol VII, Chap 1, ed. Adams et al., Wiley, NY, 1953)). The hydroxy group is treated with an allylating reagent, CH2═CHX—CH(R₈)—Y, where X is a halide or hydrogen, Y is a halide or sulfonate, and R₈ is H or (CH₂)_(v)CH₃, where v is a whole number from 0 to 4. Claisen rearrangement of the resultant allyl ether gives 4,8-dialkyl-6-allyl-7-hydroxycoumarin. The coumarins are converted to the 4,5′,8-trialkylpsoralens using one of the procedures previously described (i.e., see, Bender et al., J. Org. Chem. 44:2176 (1979); Kaufman, U.S. Pat. Nos. 4,235,781 and 4,216,154, hereby incorporated by reference). 4,5′,8-Trimethylpsoralen is a natural product and is commercially available (Aldrich Chemical Co., Milwaukee, Wis.).

[0098] Halomethylation of the 4,5′,8-trialkylpsoralens with chloromethyl methyl ether or bromomethyl methyl ether is described in U.S. Pat. No. 4,124,598, to Hearst. Longer chain 4′-(w-haloalkyl)psoralens (herein referred to as 4′-HATP) where alkyl is (CH₂)₂ to (CH₂)₁₀ can be prepared under Freidel-Crafts conditions as discussed elsewhere (Olah and Kuhn, J. Org. Chem., 1964, 29, 2317; Friedel-Crafts and Related Reactions, Vol. II, Part 2, Olah, ed., Interscience, NY, 1964, p 749). While reactions of these halomethyl-intermediates with amines (Hearst et al., U.S. Pat. No. 4,124,598, and alcohols (Kaufman,, U.S. Pat. No. 4,269,852) have been described, there are no literature reports on the formation of extended chain primary amines, especially those in which the terminal amine is linked to the psoralen by a bridge containing one or more oxygen or nitrogen atoms. Further, the properties of the latter materials, such as decreased mutagenicity are unexpected based on what is known about previously prepared compounds, such as AMT.

[0099] Starting from the 4′-HATP, reaction with an excess of a bis-hydroxy compound, HO—(B)—OH, where B is either an alkyl chain (e.g. HO—(B)—OH is 1,3-propanediol) or a monoether (e.g., diethylene glycol) or a polyether (e.g., tetraethylene glycol), either neat or with a solvent such as acetone at 20-80° C., and a base for the carbon chains longer than halomethyl, gives compound I.

[0100] The terminal hydroxy group of compound I can be transformed to an amino group under a variety of conditions (for example see Larock, ‘Comprehensive Organic Transformations”, VCH Publishers, NY, 1989). Particularly, the hydroxy group can be converted to the ester of methanesulfonic acid (structure II). This can subsequently be converted to the azide in refluxing ethanol and the azide reduced to the final amine, structure III. The method described herein utilizes triphenylphosphine and water in THF for the reduction but other methods arc contemplated.

[0101] Conversely, compound II can be reacted with diamines, H2N-(B′)-NH2 (IV) where B′ is an alkyl chain (e.g., 1,4,-butanediamine), a monoether (e.g., 3-oxo-1,5-pentanediamine) or a polyether (e.g., 3,6-dioxa-1,8-octanediamine) to give the final product, compound V. This reaction is carried out with an excess of diamine in acetonitrile at reflux, but other solvents and temperatures are equally possible.

[0102] It is recognized that alternate preparations for structures III and V are possible, for example where a linear primary alcohol is prepared which already contains the amines in a protected form and subsequently reacted with 4′-HATP in the presence of a suitable base.

[0103] Some final compounds are desired which contain an NH group in the carbon chain between the primary amino group and the psoralen ring. When the linkage between this nitrogen and the terminating nitrogen contains only CH₂ subunits and oxygen but no other nitrogens (structure VI), the product can conveniently be prepared from the (haloalkyl)psoralen and the appropriate diamine of structure IV. This method is also applicable to final products that contain more than two nitrogens in the chain (structure IX) starting from polyamines of structure VIII (e.g., norspermidine or spermine [commercially available from Aldrich, Milwaukee, Wis.]), however, in this case isomeric structures are also formed in considerable amounts. The more preferred method for the preparation of structure IX is reductive amination of the psoralen-4′-alkanal (VII) with a polyamine of structure VIII and a reducing agent such as sodium cyanoborohydride. This reductive amination is applicable to the synthesis of compounds VI as well. The carboxaldehydes (structure VII, n=0) are known (Isaacs et al., J. Labelled Cmpds. Radiopharm., 1982, 19, 345) and other members of this group can be prepared from the 4′-HATP compounds by conversion of the terminal halo group to an aldehyde functionality (for example, Durst, Adv. Org. Chem. 6:285 (1969)).

[0104] Other final products have a terminal amine linked to the psoralen by an alkyl chain. These are prepared either by reaction of the 4′-HATP with potassium phthalimide and subsequent liberation of the desired amine with hydrazine, or conversion of the 4′-HATP to the cyanide compound, followed by reduction, for example with NaBH₄-CF₃CO₂H.

[0105] The discussion of the conversion of 4,5′,8-trialkylpsoralens to 4′-aminofunctionalized-4,5′,8-trialkylpsoralens applies equally well when the 4- and/or 8-position is substituted with only a hydrogen, thus providing 4′-primaryamino-substituted-5′, (4 or 8)-dialkylpsoralens and 4′-primaryamino-substituted-5′-alkylpsoralens.

[0106] The 4,4′,8-trialkylpsoralens can be prepared in two steps starting from the 4,8-dialkyl-7-hydroxycoumarins discussed above. The coumarin is treated with an a-chloro ketone under basic conditions to give the 4,8-dialkyl-7-(2-oxoalkoxy)coumarin. Cyclization of this intermediate to the 4,4′,8-trialkylcoumarin occurs by heating in aqueous base. Under identical conditions to those described above for introducing a primaryamino-substituted side chain, the 4,4′,8-trialkylpsoralens can be converted to the 5′-(w-haloalkyl)-4,4′,8′trialkylpsoralens, (herein called 5′-HATP), (Kaufman, U.S. Pat. Nos. 4,294,822 and 4,298,614). Again, this formation of extended-chain primary amines in which the terminal amine is linked to the psoralen by a bridge containing one or more oxygen or nitrogen atoms is a novel approach.

[0107] The discussion of the conversion of 4,4′,8-trialkylpsoralens to 5′-primaryamino-substituted-4,4′,8-trialkylpsoralens applies equally well when the 4- and/or 8-position is just substituted with a hydrogen, thus providing 5′-primaryamino-substituted-4′, (4 or 8)-dialkylpsoralens and 5′-primaryamino-substituted-4′-alkylpsoralens.

[0108] Referring back to the synthesis of 4′ (or 5′)-halomethyl-4, 5′ (or 4′),8-trialkyl psoralens, the preparation of these critical intermediates in the synthesis of several compounds presents difficult challenges. The known method of preparation involves treatment of the starting psoralen with 50-200 equivalents of highly toxic, and volatile chloromethyl methyl ether or bromomethyl methyl ether. Yields of only 30-60% of the desired intermediate are obtained. Described herein, is a much improved procedure which allows for the synthesis of either isomer of the bromomethyl-trialkylpsoralens by careful control of reaction conditions.

[0109] Reaction of the 4,8-dialkyl-7-hydroxycoumarin with 2-chloro-3-butanone under typical basic conditions, provides 4,8-dialkyl-7-(1-methyl-2-oxopropyloxy)coumarin (XV). This material is heated in aqueous NaOH to provide 4,8-dialkyl-4′,5′-dimethylpsoralen (XVI). The tetrasubstitued psoralen and N-bromosuccinimide are then refluxed in a solvent, preferably with a catalyst such as benzoyl peroxide. If the solvent used is carbon tetrachloride, 4,8-dialkyl-5′-bromomethyl-4′-methylpsoralen (XVIII) is obtained in greater than 66% yield. If methylene chloride is used, only 4,8-dialkyl-4′-bromomethyl-5′-methylpsoralen (XVII) is obtained in ≧80% yield. Benzylic bromination in other solvents can also be done, generating one of the isomeric products alone or in a mixture. These solvents include, but are not limited to, chloroform, bromotrichloromethane and benzene.

[0110] The discussion above of the syntheses of 4′-primaryamino- and 5′-primaryamino-psoralens can be extended to the non-linear coumarins, specifically the isopsoralens or angelicins. Thus, the 4′-chloromethylangelicins (IXX) and the 5′-chloromethylangelicins (XX) can be prepared in a similar manner to their linear counterparts. By analogy with the synthetic pathways presented above one can envision the synthesis of 4′-(w-amino)alkylangelicins and 5′-(w-amino)alkylan gelicins where the alkyl linkage can contain one or more oxygen or nitrogen atoms.

[0111] III. Binding of Compounds to Nucleic Acid

[0112] The present invention contemplates binding new and known compounds to nucleic acid, including (but not limited to) viral nucleic acid and bacterial nucleic acid. One approach of the present invention to binding photoactivation compounds to nucleic acid is photobinding. Photobinding is defined as the binding of photobinding compounds in the presence of photoactivating wavelengths of light. Photobinding compounds are compounds that bind to nucleic acid in the presence of photoactivating wavelengths of light. The present invention contemplates methods of photobinding with photobinding compounds of the present invention.

[0113] One embodiment of the method of the present invention for photobinding involves the steps: a) providing a photobinding compound of the present invention; and b) mixing the photobinding compound with nucleic acid in the presence of photoactivation wavelengths of electromagnetic radiation.

[0114] The invention further contemplates a method for modifying nucleic acid, comprising the steps: a) providing photobinding compound of the present invention and nucleic acid; and b) photobinding the photobinding compound to the nucleic acid, so that a compound:nucleic acid complex is formed.

[0115] IV. Inactivation of Pathogens

[0116] The present invention contemplates treating a blood product with a photoactivation compound and irradiating to inactivate contaminating pathogen nucleic acid sequences before using the blood product.

[0117] A. Inactivation in General

[0118] The term “inactivation” is here defined as the altering of the nucleic acid of a unit of pathogen so as to render the unit of pathogen incapable of replication. This is distinct from “total inactivation”, where all pathogen units present in a given sample are rendered incapable of replication, or “substantial inactivation,” where most of the pathogen units present are rendered incapable of replication. “Inactivation efficiency” of a compound is defined as the level of inactivation the compound can achieve at a given concentration of compound or dose of irradiation. For example, if 100 μM of a hypothetical compound X inactivated 5 logs of HIV virus whereas under the same experimental conditions, the same concentration of compound Y inactivated only 1 log of virus, then compound X would have a better “inactivation efficiency” than compound Y.

[0119] To appreciate that an “inactivation” method may or may not achieve “total inactivation,” it is useful to consider a specific example. A bacterial culture is said to be inactivated if an aliquot of the culture, when transferred to a fresh culture plate and permitted to grow, is undetectable after a certain time period. A minimal number of viable bacteria must be applied to the plate for a signal to be detectable. With the optimum detection method, this minimal number is 1 bacterial cell. With a suboptimal detection method, the minimal number of bacterial cells applied so that a signal is observed may be much greater than 1. The detection method determines a “threshold” below which the “inactivation method” appears to be completely effective (and above which “inactivation” is, in fact, only partially effective).

[0120] B. Inactivation of Potential Pathogens

[0121] The same considerations of detection method and threshold are present when determining the sensitivity limit of an inactivation method for nucleic acid. Again, by “inactivation” it is meant that a unit of pathogen is rendered incapable of replication.

[0122] In the case of inactivation methods for material to be used by humans, whether in vivo or in vitro, the detection method can theoretically be taken to be the measurement of the level of infection with a disease as a result of exposure to the material. The threshold below which the inactivation method is complete is then taken to be the level of inactivation which is sufficient to prevent disease from occuring due to contact with the material. It is recognized that in this practical scenario, it is not essential that the methods of the present invention result in “total inactivation”. That is to say, “substantial inactivation” will be adequate as long as the viable portion is insufficient to cause disease. The inactivation method of the present invention renders nucleic acid in pathogens substantially inactivated. In one embodiment, the inactivation method renders pathogen nucleic acid in blood preparations substantially inactivated.

[0123] Without intending to be limited to any method by which the compounds of the present invention inactivate pathogens, it is believed that inactivation results from light induced binding of psoralens to pathogen nucleic acid. Further, while it is not intended that the inactivation method of the present invention be limited by the nature of the nucleic acid; it is contemplated that the inactivation method render all forms of nucleic acid (whether DNA, mRNA, etc.) substantially inactivated.

[0124] In the case of photoactivation compounds modifying nucleic acid, it is preferred that interaction of the pathogen nucleic acid (whether DNA, mRNA, etc.) with the photoactivation compound causes the pathogen to be unable to replicate, such that, should a human be exposed to the treated pathogen, infection will not result.

[0125] “Synthetic media” is herein defined as an aqueous synthetic blood or blood product storage media. In one embodiment, the present invention contemplates inactivating blood products in synthetic media. This method reduces harm to blood products and permits the use of much lower concentrations of photoactivation compounds.

[0126] The psoralen photoinactivation method inactivates nucleic acid based pathogens present in blood through a single procedure. Thus, it has the potential to eliminate bacteria, protozoa, and viruses as well. Had an effective decontamination method been available prior to the advent of the AIDS pandemic, no transfusion associated HIV transmission would have occurred. Psoralen-based decontamination has the potential to eliminate all infectious agents from the blood supply, regardless of the pathogen involved. Additionally, psoralen-based decontamination has the ability to sterilize blood products after collection and processing, which in the case of platelet concentrates could solve the problem of low level bacterial contamination and result in extended storage life. Morrow J. F., et al., JAMA 266:555-558 (1991); Bertolini F., et al., Transfusion 32:152-156 (1992). TABLE 2 Viruses Photochemically Inactivated by Psoralens Family Virus Adeno Adenovirus 2 Canine Hepatitis Arena Pichinde Lassa Bunya Turlock California Encephalitis Herpes Herpes Simplex 1 Herpes Simplex 2 Cytomegalovirus Pseudorabies Orothomyxo Influenza Papova SV-40 Paramyxo Measles Mumps Parainfluenza 2 and 3 Picorna¹ Poliovirus 1 and 2 Coxsackie A-9 Echo 11 Pox Vaccinia Fowl Pox Reo Reovirus 3 Blue Tongue Colorado Tick Fever Retro HIV Avian Sarcoma Murine Sarcome Murine Leukemia Rhabdo Vesticular Stomatitis Virus Toga Western Equine Encephalitis Dengue 2 Dengue 4 St. Louis Encephalitis Hepadna Hepatitis B Bacteriophage Lambda T2 (Rickettsia) R. Akari (Rickettsialpox)

[0127] In the article, it was pointed out that Piconaviruses were photoinactivated only if psoralens were present during virus growth.

[0128] A list of viruses which have been photochemically inactivated by one or more psoralen derivatives appears in Table 2. (From Table 1 of Hanson, C. V., Blood Cells 18:7 (1992)). This list is not exhaustive, and is merely representative of the great variety of pathogens psoralens can inactivate. The present invention contemplates the inactivation of these and other viruses by the compounds described herein. The compounds of the present invention are particularly well suited for inactivating envelope viruses, such as the HIV virus.

[0129] C. Selecting Photoctivation Compounds for Inactivation of Pathogens

[0130] In order to evaluate a compound to decide if it would be useful in the methods of the present invention, two important properties should be considered: the compound's ability to inactivate pathogens and its mutagenicity. The ability of a compound to inactivate pathogens may be determined by several methods. One technique is to perform a bacteriophage screen; an assay which determines nucleic acid binding of test compounds. A screen of this type, an R17 screen, is described in detail in EXAMPLE 9, below. Another technique is to perform a viral screen, as shown in detail in EXAMPLE 10 for HIV, and EXAMPLE 11 for Duck Hepatitis B Virus.

[0131] The R17 bacteriophage screen is believed to be predictive of HIV inactivation efficiency, as well as the efficiency of compounds against many other viruses. R17 was chosen because it was expected to be a very difficult pathogen to inactivate. It is a small, single stranded RNA phage. Without intending to be limited to any means by which the present invention operates, it is expected that shorter pieces of nucleic acid are harder to inactivate because they require a higher frequency of formation of psoralen adducts than do longer pieces of nucleic acid. Further, single stranded RNA pathogens are more difficult to inactivate because psoralens can neither intercalate between base pairs, as with double-stranded nucleic acids, nor form diadducts which function as interstrand crosslinks. Thus it is expected that when inactivation of R17 is achieved, these same conditions will cause the inactivation of many viruses and bacteria.

[0132] The second property that is important in testing a compound for use in methods of the present invention is mutagenicity. The most widely used mutagen/carcinogen screening assay is the Ames test. This assay is described by D. M. Maron and B. N. Ames in Mutation Research 113:173 (1983). The Ames test utilizes several unique strains of Salmonella typhimurium that are histidine dependent for growth and that lack the usual DNA repair enzymes. The frequency of normal mutations that render the bacteria independent of histidine (i.e., the frequency of spontaneous revertants) is low. Thus, the test can evaluate the impact of a compound on this revertant frequency.

[0133] Because some substances are not mutagenic by themselves, but are converted to a mutagen by metabolic action, the compound to be tested is mixed with the bacteria on agar plates along with the liver extract. The liver extract serves to mimic metabolic action in an animal. Control plates have only the bacteria and the extract.

[0134] The mixtures are allowed to incubate. Growth of bacteria (if any) is checked by counting colonies. A positive Ames test is one where the number of colonies on the plates with mixtures containing the compound significantly exceeds the number on the corresponding control plates.

[0135] When known carcinogens are screened in this manner with the Ames test, approximately ninety percent are positive. When known noncarcinogens are similarly tested, approximately ninety percent are negative. By performing these screens, a person skilled in the art can quickly determine which compounds would be appropriate for use in methods of the present invention.

[0136] D. Delivery of Compounds for Photoinactivation

[0137] The present invention contemplates several different formulations and routes by which the compounds described herein can be delivered in an inactivation method. This section is merely illustrative, and not intended to limit the invention to any form or method of introducing the compound.

[0138] The compounds of the present invention may be introduced in an inactivation method in several forms. The compounds may be introduced as an aqueous solution in water, saline, a synthetic media such as “Sterilyte™”, or a variety of other solvents. The compounds can further be provided as dry formulations, with or without adjuvants.

[0139] The new compounds may also be provided by many different routes. For example, the compound may be introduced to the reaction vessel, such as a blood bag, at the point of manufacture. Alternatively, the compound may be added to the material to be sterilized after the material has been placed in the reaction vessel. Further, the compounds may be introduced alone, or in a “cocktail” or mixture of several different compounds.

[0140] V. Preservation of Biochemical Properties of Material Treated

[0141] Psoralens are useful in inactivation procedures, because the reaction can be carried out at temperatures compatible with retaining biochemical properties of blood and blood products. Hanson, C. V., Blood Cells 18:7 (1992). The inactivation compounds and methods of the present invention are especially useful because they display the unlinking of pathogen inactivation efficiency from mutagenicity. The compounds exhibit powerful pathogenic inactivation without a concomitant rise in mutagenicity. The commonly known compounds tested in photoinactivation protocols, such as AMT, appear to exhibit a link between pathogen inactivation efficiency and mutagenetic action that until now seemed indivisible.

[0142] While it is not intended that the present invention be limited to any theory by which pathogen inactivation efficiency is unlinked from mutagenicity, it is postulated that unlinking occurs as a result of the length of the groups substituted on the psoralen, and the location of charges on the compounds. It is postulated that positive charges on one or both ends of mutagenic compounds have non-covalent interactions with the phosphate backbone of DNA. These interactions are presumed to occur independent of the presence of light (called “dark binding”). In theory, the psoralen thereby sterically blocks polymerase from opening up the DNA, causing mutagenicity. In contrast, compounds of the present invention carry a positive or neutral charge on a long substitute group. These substituted groups form a steric barrier during dark binding that is much easier to free from the DNA, permitting polymerase to pass. Thus no mutagenicity results.

EXPERIMENTAL

[0143] The following examples serve to illustrate certain preferred embodiments and aspects of the present invention and are not to be construed as limiting the scope thereof.

[0144] In the experimental disclosure which follows, the following abbreviations apply: eq (equivalents); M (Molar); μM (micromolar); N (Normal); mol (moles); mmol (millimoles); μmol (micromoles); nmol (nanomoles); g (grams); mg (milligrams); μg (micrograms); Kg (kilograms); L (liters); mL (milliliters); μL(microliters); cm (centimeters); mm (millimeters); μm (micrometers); nm (nanometers); J (Joules, note that in FIGS. 6, 8-17, Joules or J refers to Joules/cm²); ° C. (degrees Centigrade); TLC (Thin Layer Chromatography); EAA (ethylacetoacetate); EtOH (ethanol); HOAc (acetic acid); W (watts); mW (milliwatts); NMR (Nuclear Magnetic Resonance; spectra obtained at room temperature on a Varian Gemini 200 MHz Fourier Transform Spectrometer); m.p. (melting point); UV (ultraviolet light); THF (tetrahydrofuran); DMEM (Dulbecco's Modified Eagles Medium); FBS (fetal bovine serum); LB (Luria Broth); EDTA (ethelene diamine tetracidic acid).

[0145] For ease of reference, some compounds of the present invention have been assigned a number from 1-17. The reference numbers are assigned in FIGS. 5A-5F and appear below the structure of each compound. These reference numbers are used throughout the experimental section.

[0146] When isolating compounds of the present invention in the form of an acid addition salt, the acid is preferably selected so as to contain an anion which is non-toxic and pharmacologically acceptable, at least in usual therapeutic doses. Representative salts which are included in this preferred group are the hydrochlorides, hydrobromides, sulphates, acetates, phosphates, nitrates, methanesulphonates, ethanesulphonates, lactates, citrates, tartrates or bitartrates, and maleates. Other acids are likewise suitable and may be employed as desired. For example, fumaric, benzoic, ascorbic, succinic, salicylic, bismethylenesalicylic, propionic, gluconic, malic, malonic, mandelic, cinnamic, citraconic, stearic, palmitic, itaconic, glycolic, benzenesulphonic, and sulphamic acids may also be employed as acid addition salt-forming acids.

[0147] In one of the examples below, phosphate buffered synthetic media is formulated for platelet treatment. This can be formulated in one step, resulting in a pH balanced solution (e.g., pH 7.2), by combining the following reagents in 2 liters of distilled water: Preparation of Sterilyte ™ 3.0 Formula W. mMolarity Grams/2 Liters NaAcetate*3H₂O 136.08 20 5.443 Glucose 180.16 2 0.721 D-mannitol 182.17 20 7.287 KCl 74.56 4 0.596 NaCl 58.44 100 11.688 Na₃ Citrate 294.10 10 5.882 Na₂HPO₄*7H₂O 268.07 14.46 7.752 NaH₂PO₄*H₂O 137.99 5.54 1.529 MgCl₂*6H₂O 203.3 2 0.813

[0148] The solution is then mixed, sterile filtered (0.2 micron filter) and refrigerated.

[0149] The Polymerase Chain Reaction (PCR) is used in one of the examples to measure whether viral inactivation by some compounds was complete. PCR is a method for increasing the concentration of a segment of a target sequence in a mixture of genomic DNA without cloning or purification. See K. B. Mullis et al., U.S. Pat. Nos. 4,683,195 and 4,683,202, hereby incorporated by reference. This process for amplifying the target sequence consists of introducing a large excess of two oligonucleotide primers to the DNA mixture containing the desired target sequence, followed by a precise sequence of thermal cycling in the presence of a DNA polymerase. The two primers are complementary to their respective strands of the double stranded target sequence. To effect amplification, the mixture is denatured and the primers then to annealed to their complementary sequences within the target molecule. Following annealing, the primers are extended with a polymerase so as to form a new pair of complementary strands. The steps of denaturation, primer annealing, and polymerase extension can be repeated many times (i.e., denaturation, annealing and extension constitute one “cycle”; there can be numerous “cycles”) to obtain a high concentration of an amplified segment of the desired target sequence. The length of the amplified segment of the desired target sequence is determined by the relative positions of the primers with respect to each other, and therefore, this length is a controllable parameter. By virtue of the repeating aspect of the process, the method is referred to by the inventors as the “Polymerase Chain Reaction”. Because the desired amplified segments of the target sequence become the predominant sequences (in terms of concentration) in the mixture, they are said to be “PCR amplified”.

[0150] With PCR, it is possible to amplify a single copy of a specific target sequence in genomic DNA to a level detectable by several different methodologies (e.g., hybridization with a labelled probe; incorporation of biotinylated primers followed by avidin-enzyme conjugate detection; incorporation of ³²P labelled deoxynucleotide triphosphates, e.g., dCTP or dATP, into the amplified segment). In addition to genomic DNA, any oligonucleotide sequence can be amplified with the appropriate set of primer molecules.

[0151] The PCR amplification process is known to reach a plateau concentration of specific target sequences of approximately 10⁻⁸ M. A typical reaction volume is 100 μl, which corresponds to a yield of 6×10¹¹ double stranded product molecules.

[0152] PCR is a polynucleotide amplification protocol. The amplification factor that is observed is related to the number (n) of cycles of PCR that have occurred and the efficiency of replication at each cycle (E), which in turn is a function of the priming and extension efficiencies during each cycle. Amplification has been observed to follow the form E^(n), until high concentrations of PCR product are made. At these high concentrations (approximately 10⁻⁸ M/l) the efficiency of replication falls off drastically. This is probably due to the displacement of the short oligonucleotide primers by the longer complementary strands of PCR product. At concentrations in excess of 10⁻⁸ M, the rate of the two complementary PCR amplified product strands finding each other during the priming reactions become sufficiently fast that this occurs before or concomitant with the extension step of the PCR procedure. This ultimately leads to a reduced priming efficiency, and therefore, a reduced cycle efficiency. Continued cycles of PCR lead to declining increases of PCR product molecules. PCR product eventually reaches a plateau concentration.

[0153] The sequences of the polynucleotide primers used in this experimental section are as follows: DCD03: 5′ ACT AGA AAA CCT CGT GGA CT 3′ DCD05: 5′ GGG AGA GGG GAG CCC GCA CG 3′ DCD06: 5′ CAA TTT CGG GAA GGG CAC TC 3′ DCD07: 5′ GCT AGT ATT CCC CCG AAG GT 3′

[0154] With DCD03 as a common forward primer, the pairs generate amplicons of length 127, 327,and 1072 bp. These oligos were selected from regions that are absolutely conserved between 5 different dHBV isolates (DHBV1, DHBV3, DHBV16, DHBV22, and DHBV26) as well as from heron HBV (HHBV4).

[0155] The following examples serve to illustrate certain preferred embodiments and aspects of the present invention and are not to be construed as limiting the scope thereof.

Example 1

[0156] As noted above, the present invention contemplates devices and methods for the photoactivation of photoreactive nucleic acid binding compounds. In this example, a photoactivation device is described for decontaminating blood products according to the method of the present invention. This device comprises: a) means for providing appropriate wavelengths of electromagnetic radiation to cause photoactivation of at least one photoreactive compound; b) means for supporting a plurality of blood products in a fixed relationship with the radiation providing means during photoactivation; and c) means for maintaining the temperature of the blood products within a desired temperature range during photoactivation.

[0157]FIG. 1 is a perspective view of one embodiment of the device integrating the above-named features. The figure shows an opaque housing (100) with a portion of it removed, containing an array of bulbs (101) above and below a plurality of representative blood product containing means (102) placed between plate assemblies (103, 104). The plate assemblies (103, 104) are described more fully, subsequently.

[0158] The bulbs (101), which are connectable to a power source (not shown), serve as a source of electromagnetic radiation. While not limited to the particular bulb type, the embodiment is configured to accept an industry standard, dual bipin lamp.

[0159] The housing (100) can be opened via a latch (105) so that the blood product can be placed appropriately. As shown in FIG. 1, the housing (100), when closed, completely contains the irradiation from the bulbs (101). During irradiation, the user can confirm that the device is operating by looking through a safety viewport (106) which does not allow transmission of ultraviolet light to the user.

[0160] The housing (100) also serves as a mount for several electronic components on a control board (107), including, by way of example, a main power switch, a count down timer, and an hour meter. For convenience, the power switch can be wired to the count down timer which in turn is wired in parallel to an hour meter and to the source of the electromagnetic radiation. The count down timer permits a user to preset the irradiation time to a desired level of exposure. The hour meter maintains a record of the total number of radiation hours that are provided by the source of electromagnetic radiation. This feature-permits the bulbs (101) to be monitored and changed before their output diminishes below a minimum level necessary for rapid photoactivation.

[0161]FIG. 2 is a cross-sectional view of the device shown in FIG. 1 along the lines of 2-2. FIG. 2 shows the arrangement of the bulbs (101) with the housing (100) opened. A reflector (108A, 108B) completely surrounds each array of bulbs (101). Blood product containing means (102) are placed between upper (103) and lower (104) plate assemblies. Each plate assembly is comprised of an upper (103A, 104A) and lower (103B, 104B) plates. Tile plate assemblies (103, 104) are connected via a hinge (109) which is designed to accommodate the space created by the blood product containing means (102). The upper plate assembly (103) is brought to rest gently on top of the blood product containing means (102) supported by the lower plate (104B) of the lower plate assembly (104).

[0162] Detectors (110A, 110B, 110C, 110D) may be conveniently placed between the plates (103A, 103B, 104A, 104B) of the plate assemblies (103, 104). They can be wired to a printed circuit board (111) which in turn is wired to the control board (107).

[0163]FIG. 3 is a cross-sectional view of the device shown in FIG. 1 along the lines of 3-3. Six blood product containing means (102) (e.g., Teflon™ platelet unit bags) are placed in a fixed relationship above an array of bulbs (101). The temperature of the blood product can be controlled via a fan (112) alone or, more preferably, by employing a heat exchanger (113) having cooling inlet (114) and outlet (115) ports connected to a cooling source (not shown).

[0164]FIG. 4 is a cross-sectional view of the device shown in FIG. 1 along the lines of 4-4. FIG. 4 more clearly shows the temperature control approach of a preferred embodiment of the device. Upper plate assembly plates (103A, 103B) and lower plate assembly plates (104A, 104B) each create a temperature control chamber (103C, 104C), respectively. The fan (112) can circulate air within and between the chambers (103C, 104C). When the heat exchanger (113) is employed, the circulating air is cooled and passed between the plates (103A, 103B, 104A, 104B).

Example 2 Synthesis of 4′-(4-Amino-2-Oxa)Butyl-4,5′,8-Trimethylpsoralen Hydrochloride (Compound 2) and Related Compounds (Compound 4)

[0165] The preparation of 4′-chloromethyl-4,5′,8-trimethylpsoralen from commercially available 4,5′,8-trimethylpsolaren has been previously described. (U.S. Pat. No. 4,124,598; Isaacs et al., Biochem. 16:1058 (1977)). Reaction of the chloromethyl compound with alcohols (U.S. Pat. No. 4,124,598), pyridine (U.S. Pat. No. 4,169,204), glycol and aminoethanol (U.S. Pat. No. 4,269,852) have all been previously reported. However, compounds in which the 4′-position is substituted with a group, CH₂—X—NH₂, where X=alkyl or (poly)aza- or oxaalkyl have not been described. The synthesis of 4′-(4-amino-2-oxa)butyl-4,5′,8-trimethylpsoralen hydrochloride is achieved in four (4) steps:

[0166] STEP 1: 4′-Chloromethyl-4,5′,8-trimethylpsoralen (550 mg, 1.99 mmol) and ethylene glycol (6.8 ml, 121.9 mmol) were heated in acetone (6 mL) to 50-60° C. for 3.5 hrs. After 2 hrs heating, the white suspension had turned to a clear light yellow solution. The acetone and ethylene glycol were removed on the rotoevaporator and water (50 mL) was added to the residue. The resultant suspension was filtered, washed with cold water then dried in the vacuum oven to give 574 mg (96%) of 4′-(4-hydroxy-2-oxa)butyl-4,5′,8-trimethylpsoralen; NMR (CDCl₃) d: 2.51 (s, 6H); 2.58 (s, 3H); 3.62 (t, J=4.5 Hz, 2H); 3.78 (t, J=4.9 Hz, 2H); 4.70 (s, 2H); 6.26 (d, J=1.1 Hz, 1H); 7.61 (s, 1H).

[0167] STEP 2: 4′-(4-hydroxy-2-oxa)butyl-4,5′,8-trimethylpsoralen (574 mg, 1.9 mmol) was dissolved in CH₂Cl₂ (6 mL) under N₂ at ≦10° C. Triethylamne (359 mg, 3.55 mmol) was added. Methanesulfonyl chloride (305 mg, 266 mmol) was dropped in slowly keeping the temperature below 10° C. After addition was completed the mixture was stirred for 15 more minutes and then it was stirred at room temperature for 10 hours. To the reacted suspension CH₂Cl₂ (45 mL) was added and the mixture was washed with water (20×3 mL), then dried over anhydrous Na₂SO₄. Concentration at ≦30° C. followed by vacuum drying gave 4′-[(4-methanesulfonyloxy-2-oxa)butyl-4,5′,8-trimethylpsoralen as a yellow solid (706 mg, 98%), mp 138-140° C. NMR d 2.51 (s, 3H); 2.52 (d, 3H); 2.58 (s, 3H); 2.99 (s, 3H); 3.77 (m ,2H); 4.39 (m, 2H); 4.71 (s, 2H); 6.26(s, 1H); 7.62 (s, 1H).

[0168] STEP 3: 4′-[(4-Methanesulfonyloxy-2-oxa)butyl-4,5′,8-trimethylpsoralen (706 mg, 1.86 mmol) and sodium azide (241 mg, 3.71 mmol) were refluxed in 95% ethyl alcohol (5 mL) for 8 hours. The reaction solution was cooled and cold water (55 mL) was added. The off-white solid was filtered and washed with cold water. Upon vacuum drying, the azide was obtained as a light yellowish solid (575 mg, 95%), mp 105-106° C. NMR: d 2.51 (s, 6H); 2.58 (s, 3H); 3.41 (t, J=4.9 Hz, 2H); 3.67 (apparent t, J=4.9 Hz, 2H); 4.70 (s, 2H); 6.26 (s, 1H); 7.66 (s, 1H).

[0169] STEP 4: 4′-(4-Azido-2-oxa)butyl-4,5′,8-trimethylpsoralen (1.65 g, 5.03 mmol) was dissolved in tetrahydrofuran (10 mL). Triphenylphospine (1.59 g, 6.08 mmol) and six drops of water were added to the foregoing solution. After stirring at room temperature overnight, the light yellow solution was concentrated. The residue was dissolved in CHCl₃ (90 mL) and extracted with 0.3N aqueous HCl (30 mL, then 2×5 mL). Combined HCl layers was carefully treated with K₂CO₃ until saturated. The base solution was extracted with CHCl₃ (3×60 mL). Combined CHCl₃ layers were washed with 60 mL of water, 60 mL of brine and dried over anhydrous Na₂SO₄. Upon concentration and vacuum drying the amine was obtained as a yellow solid (1.25 g, 82%), mp 139-141° C.; NMR d 2.48 (s, 6H); 2.55 (s, 3H); 2.89 (t, J=6 Hz, 2H); 3.52 (t, J=6 Hz, 2H); 4.64 (s, 2H); 6.22 (s, 1H); 7.59 (s, 1H).

[0170] The amine was dissolved in absolute ethanol (40 mL) and 20 mL of 1N HCl in ethyl ether was added. After sitting at 5° C. overnight, the precipitate was filtered and rinsed with ether to give 1.25 g of Compound 2, mp 236° C. (decomp). Anal. Calculated for C₁₇H₂₀ClNO₄: C, 60.45: H,5.97; N, 4.15. Found: C, 60.27; H, 5.88; N, 4.10.

[0171] Similarly prepared was 4′-(5-amino-2-oxa)pentyl-4,5′,8-trimethylpsoralen, (Compound 4), m.p. 212-214° C. (decomposed). NMR of the free base: d 1.73 (pent, J=6.4 Hz, 2H), 2.45(s, 6H), 2.51 (s, 3H), 2.78 (t,J=6.8 Hz, 2H), 3.54 (t, J=6.2 Hz, 2H), 4.59 (s,2H), 6.18 (s, 1H), 7.54 (s, 1H).

Example 3 Synthesis of 4′-(7-Amino-2,5-Oxa)Heptyl-4,5′,8-Trimethylpsoralen Hydrochloride (Compound 7)

[0172] The synthesis of 4′-(7-amino-2,5-oxa)heptyl-4,5′,8-trimethylpsoralen hydrochloride proceeds in four (4) steps:

[0173] STEP 1: 4′-Chloromethyl-4,5′,8-trimethylpsoralen (589 mg, 2.13 mmol), diethylene glycol (15.4 g, 145 mmol) and acetone (13 mL) were refluxed for 11.5 hours. The reaction solution was concentrated to remove acetone and part of the diethylene glycol. To the resulting light brown solution was added CHCl₃ (40 mL), then washed with water several times. The CHCl₃ layer was dried over anhydrous Na₂SO₄ and concentrated to give 781 mg of product(˜100%). NMR d 2.46 (d, 3H), 2.47 (s, 3H ), 2.51 (s, 3H), 3.58-3.67 (m, 8H), 4.67 (s, 2H), 6.18 (s, 1H), 7.57 (s, 1H).

[0174] STEP 2: 4′-(7-Hydroxy-2,5-oxa)heptyl-4,5′,8-trimethylpsoralen (781 mg, 2.25 mmol) was dissolved in CH₂Cl₂ (2.5 mL) under a N₂ stream at <10° C. Triethylamine (363 mg, 3.59 mmol) was added. Methanesulfonyl chloride (362 mg, 3.16 mmol) was slowly dropped in to keep the temperature below 10° C. After addition was completed, the mixture was kept below 10° C. for 15 more minutes. The mixture was stirred at room temperature overnight then CH₂Cl₂ (50 mL) was added. The solution was washed with water (3×60 mL), dried over anhydrous Na₂SO₄ and concentrated at ≦30° C. Upon vacuum drying, a light brown syrup was obtained; 437 mg (76%). NMR d 2.50 (s, 3H), 2.51 (s, 3H), 2.58 (s, 3H), 3.01 (s, 3H), 3.66 (m, 4H), 3.77 (t,J=4.6 Hz, 2H), 4.37 (t, J=6 Hz, 2H), 4.69 (s, 2H), 6.25 (s, 1H), 7.61 (s, 1H)

[0175] STEP 3: 4′-(7-Methanesulfonyloxy-2,5-oxa)heptyl-4,5′,8-trimethylpsoralen (288 mg, 0.678 mmol) and sodium azide (88.2 mg, 1.36 mmol) were refluxed in 3 mL of 95% ethyl alcohol for 8 hours. The reaction solution was let cool and cold water (50 mL) was added. The water layer was poured away. The crude material was purified by chromatography on (Silica gel with chloroform eluent) a Chromatotron (Harrison Research, Inc., Palo Alto, Calif.) and vacuum dried to give a light yellow syrup, (123 mg, 49%). NMR d 2.50 (s, 6H), 2.57 (s, 3H ), 3.39 (t, J=5.2 Hz, 2H), 3.68 (m, 6H), 4.70 (s, 2H), 6.24 (s, 1H), 7.62 (s, 1H)

[0176] STEP 4: 4′-(7-Azido-2,5-oxa)heptyl-4,5′,8-trimethylpsoralen (122 mg, 0.33 mmol), triphenylphosphine (129 mg, 0.49 mmol) and several drops of water were dissolved in tetrahydrofuran (2 mL). The light yellow clear solution was stirred at room temperature over a weekend; no starting material was detected by TLC. The reaction solution was concentrated and the residue was dissolved in CHCl₃ (20 mL). The solution was extracted with 0.15 N aqueous HCl solution (10 mL then 2×5 mL) and the HCl layers was taken to pH 13 by addition of 20% aqueous NaOH solution. The basic solution was extracted with CHCl₃ (3×15 mL). The combined CHCl₃ layers were washed with water, dried over anhydrous Na₂SO₄, concentrated, and vacuum dried to give 63.9 mg of product (56%). TLC showed only one spot. NMR d 2.50 (s, 3H); 2.50 (s, 3H); 2.57 (s, 3H); 2.86 (t, J=5.3 Hz, 2H); 3.50 (t, J=5.3 Hz, 2H); 3.63 (s, 4H); 4.70 (s, 2H); 6.24 (s, 1H); 7.62 (s, 1H). m.p. 170-173° C.

[0177] The solid was dissolved in absolute ethanol, then 1M HCl in ethyl ether was added, the suspension was filtered and the product rinsed with ether and dried.

Example 4 Synthesis of 4′-(12-Amino-8-Aza-2,5-Dioxa)dodecyl-4,5′,8-Trimethylpsoralen Dihydrochloride (Compound 8)

[0178] The synthesis of 4′-(12-amino-8-aza-2,5-dioxa)dodecyl-4,5′,8-trimethylpsoralen dihydrochloride proceeds in one (1) step from the product of Example 3, step 2: A solution of 4′-(7-methanesulfonyloxy-2,5-oxa)heptyl-4,5′,8-trimethylpsoralen (108 mg, 0.253 mmol) in 8 mL of acetonitrile was slowly added to a solution of 1, 4-diaminobutane (132 mg, 1.49 mmol) in 2.8 mL of acetonitrile. After refluxing for 8 hours, no starting material remained by TLC. The reaction mixture was cooled to room temperature and CHCl₃ (25 mL) and 1 N aqueous NaOH (25 mL) solution were added. The layers were separated and CHCl₃ (2×10 mL) was used to wash the aqueous layer. Aqueous HCl (0.3 N , 3×10 mL) was used to extract the product from the combined organics layers. The HCl layers was treated with 20% aqueous NaOH solution until pH 13. The combined basic layers were then extracted with CHCl₃ (3×20 mL). The CHCl₃ layer was washed with saturated NaCl aqueous solution (10 mL) then dried over anhydrous Na₂SO₄. After concentration and vacuum drying, 63 mg of product was obtained (60%). NMP d 1.45 (m, 2H), 2.49 (s, 6H), 2.55 (s, 3H), 2.58 (t, 2H), 2.66 (t, J=5.6 Hz, 2H), 2.76 (m, 4H), 3.55-3.61 (m, 6H), 4.68 (s, 2H), 6.22 (s, 1H), 7.61 (s, 1H).

Example 5 Synthesis of 4′-(2-Aminoethyl)-4,5′,8-Trimethylpsoralen Hydrochloride (Compound 3)

[0179] The synthesis of 4′-(2-aminoethyl)4,5′,8-trimethylpsoralen proceeds in one (1) step: sodium trifluoroacetoxyborohydride was made by adding trifluoroacetic acid (296 mg, 2.60 mmol) in 2 mL of THF to a stirred suspension of sodium borohydride (175 mg, 4.63 mmol) in 2 mL of THF over a period of 10 minutes at room temperature. The resultant suspension was added to a suspension of 4′-cyanomethyl-4,5′,8-trimethylpsoralen (Kaufman et al., J. Heterocyclic Chem. 19:1051 (1982)) (188 mg, 0.703 mmol) in 2 mL of THF. The mixture was stirred overnight at room temperature. Several drops of water were added to the reacted light yellow clear solution to decompose the excess reagent under 10° C. The resulting mixture was concentrated and 1 N aqueous NaOH solution (30 mL) was added. Chloroform (30 mL then 10 mL, 5 mL)) was used to extract the resultant amine. Combined CHCl₃ layers were washed with saturated NaCl solution. The amine was then extracted into aqueous 0.3 N HCl (10, 5, 5 mL) and the acid layers were taken to pH 13 with 20% aqueous NaOH. CHCl₃ (3×10 mL) was used to extract the amine from the combined base layers then washed with water (2 mL) and dried over anhydrous Na₂SO₄. Upon concentration and vacuum drying the amine was obtained as a solid, >95% pure by NMR. NMR d 2.45 (s, 3H); 2.47 (s, 3H); 2.53 (s, 3H); 2.78 (t, J=6.6 Hz, 2H); 3.00 (t, J=6.5 Hz, 2H); 6.20 (s, 1H); 7.44 (s, 1H). The solid was dissolved in absolute ethanol. A solution of hydrogen chloride in diethyl ether (1 N, 1 mL) was added. TABLE 10(B) AMT TA102 ‘TA102 TA1537 TA1537 TA1538 TA1538 Dose STRAIN μg/plate −S9 +S9 −S9 +S9 −S9 +S9  0 346 404 9 9 15 19  n = 26  n = 41  n = 30 n = 45  n = 30 n = 42  0.1  27 −20 0 2  3 3 n = 3 n = 6 n = 3 n = 6  n = 3 n = 6   0.5  47 5 3 2  4 13 n = 3 n = 6 n = 9 n = 12 n = 9 n = 12  1  88 −17 5 3  4 37 n = 3 n = 6 n = 9 n = 12 n = 9 n = 12  5 266 51 44 22 13 177 n = 3 n = 6 n = 9 n = 12 n = 18 n = 21  10 52 30 14 255 n = 9 n = 9 n = 9 n = 9   50 2688 94 n = 9 n = 9  100 2058 686 n = 9 n = 9  250 434 3738 n = 9 n = 12 100 μg/pl 10 μg/plt 10 μg/ 5 μg/plate plt Positive hydrogen 9-Amino 2- 2-Amino- Amino- Control peroxide acridine fluorene fluorene 660 284 73 1064  n = 23 n = 6 n = 24 n = 30

[0180] TABLE 11(A) 8-MOP TA102 TA102 TA1537 TA1537 Dose STRAIN μg/plate −S9 +S9 −S9 −S9  0 346 404 9 9 n = 26 n = 41  n = 30  n = 45  1 −55 −46 n = 14 n = 17  10 −57 −27 n = 14 n = 17  30 5 1 n = 3 n = 6  60 3 1 n = 3 n = 6  90 −1 −4 n = 3 n = 6 100 217 290 n = 14 n = 17 500 781 1179 n = 11 n = 11 100 μg/plt 10 μg/plt 10 μg/plt Positive hydrogen 9-Amino- 2-Amino- Control peroxide Acridine fluorene 660 284 73 n = 23 n = 6  n = 24

[0181] TABLE 11(B) 8-MOP TA102 TA102 TA1537 TA1537 Dose STRAIN μg/plate −S9 +S9 −S9 +S9  0 346 404 9 9 n = 26 n = 41  n = 30  n = 45  1 −55 −46 n = 14 n = 17  10 −57 −27 n = 14 n = 17  30 5 1 n = 3 n = 6  60 3 1 n = 3 n = 6  90 −1 −4 n = 3 n = 6 100 217 290 n = 14 n = 17 500 781 1179 n = 11 n = 11 100 μg/plt 10 μg/plt 10 μg/plt Positive hydrogen 9-Amino- 2-Amino- Control peroxide Acridine fluorene 660 284 73 n = 23 n = 6  n = 24

[0182] TABLE 12 Compound 1 TA100 TA100 TA1538 TA1538 Dose STRAIN μg/plate −S9 +S9 −S9 +S9  0 126 123 15  19 n = 41  n = 56  n = 30  n = 42  5 292 −24 10  21 n = 3  n = 3 n = 3 n = 3 10 337 −22 12  22 n = 3  n = 3 n = 3 n = 3 Positive 1.5 μg/plate 5 μg/plate Control Sodium 2-Amino- Azide fluorene 965 1064 n = 38  n = 30

[0183] TABLE 13(A) Compound 2 TA1537 TA1537 TA1538 TA1538 Dose STRAIN μg/plate −S9 +S9 −S9 +S9  0  9  9 15 19  n = 30  n = 45  n = 30  n = 42  5 −8 2 n = 3 n = 3  10  36  5 −13 4 n = 3 n = 3 n = 3 n = 3  50 282  40 n = 3 n = 3 100 258  88 n = 3 n = 3 250 176 744 n = 3 n = 3 500 114 395 n = 3 n = 3 10 μg/plt 10 μg/plt 5 μg/plate Positive 9-Amino- 2-Amino- 2-Amino- Control acridine fluorene fluorene 284  73 1064 n = 6  n = 24  n = 30

[0184] TABLE 13(B) Compound 2 TA1537 TA1537 TA1538 TA1538 Dose STRAIN μg/plate −S9 +S9 −S9 +S9  0  9  9 15 19  n = 30  n = 45  n = 30  n = 42  5 −8 2 n = 3 n = 3  10  36  5 −13 4 n = 3 n = 3 n = 3 n = 3  50 282  40 n = 3 n = 3 100 258  88 n = 3 n = 3 250 176 744 n = 3 n = 3 500 114 395 n = 3 n = 3 10 μg/plt 10 μg/plt 5 μg/plt Positive 9-Amino- 2-Amino- 2-Amino- Control acridine fluorene fluorene 284  73 1064 n = 6  n = 24  n = 30

[0185] TABLE 14 Compound 3 TA100 TA100 TA1538 TA1538 Dose STRAIN μg/plate −S9 +S9 −S9 +S9  0 126 123 15 19  n = 41  n = 56  n = 30  n = 42  5  47 −19 0 1 n = 3 n = 3 n = 3 n = 3 10  47 8 −6 9 n = 3 n = 3 n = 3 n = 3 1.5 μg/plt 5 μg/plt Positive Sodium 2-Amino- Control Azide fluorene 965 1064  n = 38  n = 30

[0186] TABLE 15 Compound 4 TA100 TA100 TA1538 TA1538 Dose STRAIN μg/plate −S9 +S9 −S9 +S9  0 126 123 15 19  n = 41  n = 56  n = 30  n = 42  5 −41 −10 −2 7 n = 3 n = 3 n = 3 n = 3 10 3 −3 −2 −2 n = 3 n = 3 n = 3 n = 3 1.5 μg/plate 5 μg/plate Positive Sodium 2-Amino- Control Azide fluorene 965 1064  n = 38  n = 30

[0187] TABLE 16(A) STRAIN Compound 6 Dose TA98 TA98 TA100 TA100 μg/plate −S9 +S9 −S9 +S9 0 20 25 126 123 n = 38 n = 53 n = 41 n = 56 5 −32 12 n = 3 n = 3 10 12 −5 3 −5 n = 3 n = 3 n = 9 n = 9 50 12 2 2 24 n = 3 n = 3 n = 6 n = 6 100 22 20 −18 −2 n = 6 n = 6 n = 6 n = 6 250 12 40 −38 n = 3 n = 3 n = 3 500 9 52 n = 3 n = 3 5 μg/plate 1.5 μg/plate Positive 2-Amino- Sodium Control fluorene Azide 1154 965 n = 35 n = 38

[0188] TABLE 16(B) STRAIN Compound 6 Dose TA1537 TA1537 TA1538 TA1538 μg/plate −S9 +S9 −39 +S9 0 9 9 15 19 n = 30 n = 45 n = 30 n = 42 5 −5 0 n = 3 n = 3 10 141 −1 −2 8 n = 6 n = 6 n = 3 n = 3 50 2010 17 n = 6 n = 6 100 795 35 n = 6 n = 6 250 228 99 n = 6 n = 6 500 43 369 n = 3 n = 3 10 μg/plate 10 μg/plate 5 μg/plate Positive 9-Amino- 2-Amino- 2-Amino- Control acridine fluorene fluorene 284 73 1064 n = 6 n = 24 n = 30

[0189] Maron and Ames (1983) describe the conflicting views with regard to the statistical treatment of data generated from the test. In light of this, this example adopts the simple model of mutagenicity being characterized by a two-fold or greater increase in the number of revertants above background (in bold in the tables), as well as dose dependent mutagenic response to drug.

[0190] With regard to 8-MOP, the only mutagenic response detected was a weak base-substitution mutagen in TA102 at 500 μg/plate (TABLE 14 (B)).

[0191] In sharp contrast, AMT (TABLE 13 (A) and 13 (B)) showed frameshift mutagenicity at between 5 and 10 μg/plate in TA97a and TA98, at 5 μg/plate in TA1537 and at 1 μg/plate in TA1538. AMT showed no significant base-substitution mutations.

[0192] Looking at Compound 1, the only mutagenic response detected was a weak frameshift mutagen in TA1538 at 5 μg/plate in the presence of S9. Compound 1 also displayed mutation in the TA100 strain, but only in the absence of S9. Compound 2 also showed weak frameshift mutagenicity in the presence of S9 in TA98 and TA1537. Compounds 3 and 4 showed no mutagenicity. Compound 6 had no base substitution mutagenicity, but showed a frameshift response in TA98 in the presence of S9 at concentrations of 250 μg/plate and above. It also showed a response at 50 μg/plate in TA1537 in the presence of S9. Both responses are significantly below that of AMT, which displayed mutagenicity at much lower concentrations (5 μg/plate).

[0193] From this data it is clear that the compounds of the present invention are less mutagenic than AMT, as defined by the Ames test. At the same time, these compounds show much higher inactivation efficiency than 8-MOP, as shown in Examples 9 and 13. These two factors support that the compounds of the present invention combine the best features of both AMT and 8-MOP, high inactivation efficiency and low mutagenicity.

Example 15

[0194] In Example 12, the compounds of the present invention exhibited the ability to inactivate pathogens in synthetic media. This example describes methods by which synthetic media and compounds of the present invention may be introduced and used for inactivating pathogens in blood. FIG. 20A schematically shows the standard blood product separation approach used presently in blood banks. Three bags are integrated by flexible tubing to create a blood transfer set (200) (e.g. commercially available from Baxter, Deerfield, Ill.). After blood is drawn into the first bag (201), the entire set is processed by centrifugation (e.g., Sorvall™ swing bucket centrifuge. Dupont), resulting in packed red cells and platelet rich plasma in the first bag (201). The plasma is expressed off of the first bag (201) (e.g., using a Fenwall™ device for plasma expression), through the tubing and into the second bag (202). The first bag (201) is then detached and the two bag set is centrifuged to create platelet concentrate and platelet-poor plasma; the latter is expressed off of the second bag (202) into the third bag (203).

[0195]FIG. 20B schematically shows an embodiment of the present invention by which synthetic media and photoactivation compound are introduced to platelet concentrate prepared as in FIG. 20A. A two bag set (300) is sterile docked with the platelet concentrate bag (202) (indicated as “P.C.”). Sterile docking is well-known to the art. See e.g., U.S. Pat. No. 4,412,835 to D. W. C. Spencer, hereby incorporated by reference. See also U.S. Pat. Nos. 4,157,723 and 4,265,280, hereby incorporated by reference. Sterile docking devices are commercially available (e.g., Terumo, Japan).

[0196] One of the bags (301) of the two bag set (300) contains a synthetic media formulation of the present invention (indicated as “STERILYTE”). In the second step shown in FIG. 20B, the platelet concentrate is mixed with the synthetic media by transferring the platelet concentrate to the synthetic media bag (301). The photoactivation compound can be in the bag containing synthetic media (301), added at the point of manufacture. Alternatively, the compound can be mixed with the blood at the point of collection, if the compound is added to the blood collection bag (FIG. 20A, 201) at the point of manufacture. The compound may be either in dry form or in a solution compatable with the maintainance of blood.

[0197]FIG. 20C schematically shows one embodiment of the decontamination approach of the present invention applied specifically to platelet concentrate diluted with synthetic media as in FIG. 20B. In this embodiment, platelets have been transferred to a synthetic media bag (301). The photoactivation compound either has already been introduced in the blood collection bag (201) or is present in the synthetic media bag (301) to which the platelets are now transferred. This bag (301), which has UV light transmission properties and other characteristics suited for the present invention, is then placed in a device (such as that described in Example 1, above) and illuminated.

[0198] Following phototreatment, the decontaminated platelets are transferred from the synthetic media bag (301) into the storage bag (302) of the two bag set (300). The storage bag can be a commercially available storage bag (e.g., CLX bag from Cutter).

[0199] It is to be understood that the invention is not to be limited to the exact details of operation or exact compounds, composition, methods, or procedures shown and described, as modifications and equivalents will be apparent to one skilled in the art. 

We claim:
 1. A psoralen compound, comprising: a) a substituent R₁ on the 5′ carbon atom, selected from the group consisting of: —(CH₂)_(u)—NH₂ —(CH₂)_(w)—R₂—(CH₂)_(z)—NH₂, —(CH₂)_(w)—R₂—(CH₂)_(x)—R₃—(CH₂)_(z)—NH₂, and —(CH₂)_(w)—R₂—(CH₂)_(x)—R₃—(CH₂)_(y)—R₄—(CH₂)_(z)—NH₂; wherein R₂, R₃, and R₄ are independently selected from the group consisting of O and NH, and in which u is a whole number from 3 to 10, w is a whole number from 1 to 5, x is a whole number from 2 to 5, y is a whole number from 2 to 5, and z is a whole number from 2 to 6; and b) substituents R₅, R₆, and R₇ on the 4, 4′, and 8 carbon atoms respectively, independently selected from the group consisting of H and (CH₂)_(v)CH₃, where v is a whole number from 0 to 5, and wherein when R₁ is —(CH₂)₂—NH₂, R₆ is H; or salts thereof.
 2. A psoralen compound, comprising: a) a substituent R₁ on the 5′ carbon atom, selected from the group consisting of: —(CH₂)_(w)—R₂—(CH₂)_(z)—NH₂, —(CH₂)_(w)—R₂—(CH₂)_(x)—R₃—(CH₂)_(z)—NH₂, and —(CH₂)_(w)—R₂—(CH₂)_(x)—R₃—(CH₂)_(y)—R₄—(CH₂)_(z)—NH₂; wherein R₂, R₃, and R₄ are independently selected from the group consisting of O and NH, and w is a whole number from 1 to 5, x is a whole number from 2 to 5, y is a whole number from 2 to 5, and z is a whole number from 2 to 6; and b) substituents R₅, R₆, and R₇ on the 4, 4′, and 8 carbon atoms respectively, independently selected from the group consisting of H and (CH₂)_(v)CH₃, where v is a whole number from 0 to 5; or salts thereof. 